from perlfaq5...

For passing filehandles to functions, the easiest way is to preface them with a star, as in func(*STDIN). See the section on Passing Filehandles in the perlfaq7 manpage for details.

from perlfaq7...

How can I pass/return a {Function, FileHandle, Array, Hash, Method, Regexp}?
With the exception of regexps, you need to pass references to these objects. See the section on Pass by Reference in the perlsub manpage for this particular question, and the perlref manpage for information on references.